FIG. 1 shows a prior art module before assembly.
A LED lamp has a lamp body 14 and two extension leads 11, 12. LED chip 10 has a top electrode and a bottom electrode. The chip 10 is mounted on the top of the first lead 11 and electrically couples its bottom electrode to the lead 11. The top electrode of the chip 10 is wire-bonded to the second lead 12 through a metal wire 13. Ring pads 165 are on the bottom side of the substrate 16 and surround each of the corresponding plated through holes 161.
FIG. 2 shows the prior art module after assembly.
After the insertion of the two leads 11, 12 into the corresponding plated through holes 161, the leads 11, 12 are electrically coupled to the corresponding metal lines 164 on the substrate 16. The metal lines 164 are coupled to power supply source for energizing the LED lamp. Solders 162 are used for jointing the ends of the leads to the pad 165.
The drawback for the conventional art is that an air gap 163 exists between the bottom side of the lamp body 14 and the metal line 164. Moisture may enter the air gap 163, causing either oxidation of the metal lines 164 and/or to the leads 11, 12, or short-circuit between the leads 11, 12 to impair the lifetime of the LED lamp.